Scientists Look for Answers as More US Girls Enter Puberty at an Earlier Age

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This is the VOA Special English Health Report.

A mother in Washington noticed something unusual one day, just before her daughter's eighth birthday. She thought her daughter was developing breasts. When they went for the girl's yearly check-up, she asked the doctor if she was right. And the doctor said the girl had breast buds. Last year a study in Denmark reported an increase in early breast development. Now a new study in the journal Pediatrics adds to evidence of an increase in early puberty in American girls. The study took place in three big cities. Dr. Frank Biro at Cincinnati Children's Hospital Medical Center in Ohio led the study. He says it began about seven years ago.Researchers studied a group of about one thousand two hundred girls to see when they would begin puberty. Dr. Biro says the study found that white girls had the greatest increase in rates of breast development. The rates, he says, were about twice as high for seven- and eight-year-olds compared to earlier studies. At age seven, the rates were ten percent of whites, twenty-three percent of blacks and fifteen percent of Hispanics.Dr. Biro says girls with a higher body mass index are more likely to enter puberty early. Body mass index, or BMI, is a measure of weight in relation to height. But the nation's increase in overweight children may be only part of the explanation. The researchers have been collecting blood and urine samples from the girls for testing. Dr. Biro says the tests are to look for chemicals from the girls' environment that could affect growth.He says these chemicals might act like natural hormones that the body makes. Or the chemicals might interfere with how those hormones act on the body.He says these chemicals could include growth hormones fed to farm animals. But they could also include chemicals such as phthalates. These are used to makes some kinds of plastics and other products. Dr. Biro says personal care products contain chemicals that could affect the timing of maturation or other body functions.But researchers must wait for all the girls to enter puberty before they can understand the effects of environmental chemicals.Dr. Biro says less research has been done to look for early puberty in boys. But he says some studies have shown that a higher BMI does not speed up development in boys, and may even slow it. And that's the VOA Special English Health Report.